She goes briefly stiff upon hearing about the crest worms, everything off about this Rin finally clicking into place. Kariya had told her what they were, of Sakura's plight, and her connection to Rin when she first came to the Tower. She had not said anything before, believing it to be a private matter and swearing to protect Sakura should she come here as a friend of Shirou's.

But hearing of those vile worms made some of this Rin's situation make sense. She could see Rin insisting upon being sent to the Matou residence in Kariya's place or her father deciding to send her instead of Sakura.

She kept her back to her only turning her head a bit to look at her.

"Thank you for understanding. Unfortunately, I do not know the full process for creating these bodies, nor what else is in them."

She could feel the anger toward the Matou family beginning to burn for allowing Rin to be violated in such a way as well. However, Rin had her pride and Arturia knew that trying to force anything upon her when the only information she had was the bare basics would not help either of them at all. Arturia also knew this Rin had little reason to trust her at this point. Perhaps she would ask further if Rin ever came to see her as an ally in much the way Arturia saw the Rin Tohsaka she had known.

For now, though, she would keep a lookout for the girl who wore an ally's face from a distance and aid her if Arturia absolutely knew she needed it.